Conventionally, for many years, fuel injectors for heavy duty diesel engines, such as used for example in 12 liter displacement truck engines have been designed to deliver fuel at pressures ranging from 8,000-20,000 psi to the engine's combustion chambers. These are fairly high pressures and have required considerable engineering attention in insuring structural integrity of the injector, good sealing properties, and effective atomization of the diesel fuel within the combustion chamber. However, increasing demands on greater fuel economy, cleaner burning, fewer missions, and Nox control at placed even higher demands on the engine 's fuel delivery system. One means of meeting these demands is to significantly increase the fuel pressure within the injector to as much as 28,000 psi. In terms of developing these pressures within the injector, the task is fairly simple. Since this is largely a matter of proportioning the ratio of the diameter of the primary fuel chamber and pressure inducing reciprocating plunger to the force being delivered to the plunger. Earliest attempts with such a re-design have, however, proved less than satisfactory since increased loads on the plunger as its in compression bearing the compression stroke result in the plunger elastically radially expanding through its compressed length. This expansion on the compression reduces the clearance between the plunger and the plunger cylinder walls, causing scoring, premature wear and ultimately loss of an effective seal between the plunger and the adjacent plunger cylinder wall.
While this problem could be addressed in any number of ways such as a different selection of parts materials, the present invention is directed toward maintaining overall design efficiencies and design parameters which have proved their reliability over the years, and to reconstruct the plunger in such a manner that it can transmit the required loads free of any elastic radial expansion capable of causing interference with the plunger cylinder wall and yet maintaining the same type sealing characteristics of conventional plunger/injector design.